For modern communication system based on infrared-light transmission, signal conditioning with minimum data loss is a major specification. This signal conditioning may also become an issue in many cases when input light pulses with extended amplitude range may be converted to a current or voltage signal and then amplified by a fixed gain. In fact, the minimum detectable signal itself fixes the gain but also determines the maximum amplitude of an input signal before an amplifier is pushed into deep non-linear operation and saturation.
A realization of a limiting network to be used in these cases simply comprises two Schottky diodes and a current limiting resistor. Such a limiting network is intended to avoid deep saturations in sensible parts of a protected circuit. It employs an input limiting mechanism to force a required output voltage. Otherwise, a direct output limiting mechanism is used. In these cases the protection of the circuit is activated in case of a fault, as well as in case of an unforeseen operating condition, and it prevents damages to the circuit itself.
Such a protected circuit cannot operate correctly (no linear conditions being provided) as long as the limiting network is functional. Nevertheless, a clamped overdrive recovery time should be at least an order of magnitude faster than the amplifier's normal saturation recovery time, thus allowing rapid resumption of linear operation.
In particular, in digital communication systems dealing with the so called OOK [On-Off Keying] data type, a receiver output stage is pushed to the edge of saturation by normal input drive conditions so as to swing between rails. When an overdrive occurs, the saturation of the output stage becomes an issue because, depending on an overdrive level, it may be pushed far beyond the saturation edge, thus leading to light pulse misdetection and fault in the communication.
The saturation level is usually controlled by using a control loop that acts on the gain of the receiver, adjusting it according to necessity. Such an approach may not be applied when an open loop amplification chain is to be used.
Moreover, the known approaches cannot always correctly operate in case of an amplifier input signal having a wide range, and little data loss may not be guaranteed at higher levels of such an input signal. The technical issue underlying the approach presented in the present application is that of providing an overdrive control system having structural and functional characteristics which allow the widening of the amplifier input range without deep changes in the amplifier architecture, and to help reduce data loss at higher levels of the amplifier input signal, in this way overcoming the limits which still affect the devices realized according to the prior art.